Permanent magnet hammer module in high speed printers



H. R. BARNES Nov. 10, 1964 PERMANENT MAGNET HAMMER MODULE IN HIGH SPEEDPRINTERS Filed Sept. 18, 1961 INVENTOR.

HUGH R. BAR/V5.5

ATTORNEY IPERMANENT 'MAGNETJHAMMER MODULE I l j l INHIGH SPEEDPRINTERS VHugh R.'"Barnes', St; Clair Shores, Mich, assiguor, by

mesne assignments, to Holley Computer 'ProdnctsCom -pany;Warren,-Mich.,.a-corporation of Michigan Filed Sept. 18, 1961, Ser.N0.-138,99 1--;

. 3 Clairns. ((31,.101-93).

.This invention relates to speedl printers', andtp'articularly. tovnovel electromechanical, OH-thCrflY. type printer.. 1 I.

More specifically,thisinvention relatesto ajmodification. of the print.hammerme'chanism. disclosed mus;

, Printer, and-filedon September.;14,. 1961, in.the-n'ames,,

application Serial,No. 138,157, entitled .HighgSpeed of Arvin D.McGregor'and, James M. Irvine, Jr. f

.In the-.abovereferenced. application, the, disclosure or whichishereby. incorporated by reference each print hammer 160112111 associatedtherewith electromagnet, 226.comprising two.windings,..one .of thewindings being,

termeda holding coil andthe otherwinding being termed a pulse. coil .Theholding (foil was, continuously energized whenever the .p'rinter powerwas turnedljofrn, and. the purpose thereof was to hold the print hammer.interposer mechanism .in. the. non-print position,.Additionallyaddressing any givenprint hammer forprinting inf,

volved energizing the pulse coil of the electromagnet associated withthatp'articular ,ha'rnrnerso as to cancel out the magnetic field oftheholding coiland thereby permit the hammer 'interposer system to move tothe print position. The-printer disclosed in the above referenced""applicationalso containeda bail bar '243,the purpose of whichwas to return the hammer interposer system'to 'the-non-printpositionupon the shut-down theprinter and immediately'upon restarting theprinter;

The main-feature of-this invention is the substitution of a permanentmagnetfor the holding coil in the print hammer mechanism disclosed'inthe above referenced application. t s 1 Accordingly, one object of theinvention is to provide a print hammer mechanism in which no exteriorsource of electrical power is required to hold the print hammerinterposer system in the non-print position.

Another object of the invention is to provide a print hammer mechanismin which the printer interposer system is held in the non-print positioneven with the printer power turned off, thus making it possible toeliminate the bail bar and all elecrtonic and mechanical partsassociated with the bail bar.

Another object of the invention is to provide a print hammer mechanismwhich is relatively inexpensive to construct and less likely to requirerepair. 7

These and other objects of the invention will become more apparent uponreference to the following specification and the attached drawingswherein:

FIGURE 1 is a fragmentary part elevational and part cross-sectional viewillustrating a print hammer mechanism embodying the invention;

FIGURE 2 is a cross-sectional view taken on the plane of line 22 ofFIGURE 1 and looking in the direction of the arrows;

FIGURE 3 is a fragmentary cross-sectional view taken on the plane ofline 33 of FIGURE 1 and looking in the direction of the arrows.

Referring now to the figures in greater detail, FIGURE 1 is a view verysimilar to FIGURE 6 of the above referenced application, and allelements common with those in the above FIGURE 6 will be identified withthe same reference numbers. Thus, the'hammer module assembly 196', whichmay be completely interchangeable with module 1% of application SerialNo. 138,157, comprises a base plate 197 on which the four hammeractuating levers 215 are' mounted, As before, each lever 215 has an arm219.cooperating with the free end of the interposerlever 1822, sometimesreferred to as a beaver tailv 182, whi'ch is pivotally connected to theprint hammer 160. ,The spring 186 urges the be'avertail 182 downwardlyso that a lobe 241 of thecam 168 may impact the beaver tail 182and'dri've the hammer 160 into the print drum 109 when the hammer isaddressed for printing.

As explained in the aboyereferenced application, each actuating lever215has a second arm to which there is attachedan armature224, thearmaturebeing provided? to holdthe actuating lever 215, and thus thebeaver tail;

andhammerassembly, in the non-print position until the.

hammer isv addressed. 1

,In, the Serial 110,138,157 construction, each hammer k beavertail132and actufatingjlever 215' comprised an inj tel-poser system andhadassociated therewith an GlCCiIfQ-f magnetf226 having two windings, aholding coil which is continuously energizedand a pulse coil which isenergized' only when the hammer in question was addressed for'printingso as to releasethe armature 224 and allow the spring 186 to moye 'theinterposer system into the '1 path of the] cam 108.

1n th'e modified construction in FIGURE S l I and 2,'the electromagnetassociated with each of the hammer mechanisms isreplaced by acombination perj manent magnet. and pulse coilassembly 10. The fourassemblies 111, are mounted on the base plate.197 in an arcuate patternjust as the 'electromagnets 226 were "mounted, and each assemblylqincludes a permanent magnet 12 of predetermined magnetic force and asuitably formed pole piece 14 mounted on the magnet'in magnet, the edges16 and 17 of whichattract and hold thejarmature 224 of the actuatinglever 215 in the:

position shown in FIGURE 1 against the force of the spring 186. Edge 16is on the pole piece, while edge 1'? is provided by an opening 19 in thebase plate 197.

A pulse coil 18 is mounted on the leg 20 of the pole piece 14. Thepermanent magnet 12, to which the pole piece 14 is attached, provides aforce of attraction which holds the armature 224 of the lever interposersystem in a non-print position against the leg 26 The pulse coil 13 iswound in a particular direction so that when current is passed throughthe coil 18, the resultant magnetic field is in a direction opposite tothat of the magnetic field of the permanent magnet 12. This serves to,decrease the magnetic field in the pole piece 14 and in the armature 224to the extent that the force of the spring 186 now exceeds the magneticforce and is thus capable of pivoting the actuating lever 215, andhence, the armature 224, away from the pole piece 14.

With the exception of the above specific construction described above,the other remaining details of the hammer module 1% shown herein may beexactly the same as that of the hammer module 196 disclosed inapplication Serial No. 138,157. This being so, the hammer module 196'could be substituted directly for the hammer module 1% of the abovereferenced application.

piece 14 is a part of a permanent horseshoe magnet haviug sufficientstrengthto retain the armature 224 against P t nt d w- 10, 4;

the force of the spring 185, the armature 224- will be retained by thepole piece until the pulse coil 18 is energized when it is desired thatthat particular hammer print a character, this being accomplished in thesame manner as described in Serial No. 138,157. When coil 18 isenergized, thus cancelling the holding force of the permanent magnet inthe manner described above, the armature 224 is released and the spring186 pulls the interposer assembly comprised of the actuator lever 215and the beaver tail 182 downwardly to the stop 21 so that a cam lobe 241may strike the surface 183 of the beaver tail, after which the nextsucceeding cam lobe will strike surface 242 of the arm 219 and rotatethe actuator lever 215 to the non-print position.

With this modified construction, it is apparent that no external poweris required to energize a separate holding coil when the printer isturned on or off. Since the permanent magnets 12 provide a permanentholding force that exists even when the printer is turned off, all ofthe actuating levers 215 will be in the non-print position shown inFIGURE 1 at all times, except when the pulse coil 18 is energized.Momentum or the inertia of the cam 103 at the end of the print cyclewill return all actuating levers to the FIGURE 1 position before theprinter is turned off; thus, the bail bar 243 provided in the printerdisclosed in application Serial No. 138,157 and all the parts associatedtherewith are not required and can be eliminated to reduce the overallcost of the printer. Since all of the actuating levers will be retainedin the non-print position at all times when the printer is shut off, itis apparent that meaningless lines of print will not occur when theprinter is subsequently turned on.

It should be apparent that certain modifications may be made withoutexceeding the scope of the following claims.

What I claim as my invention is:

1. In an electromechanical printer having a print drum, a movable printhammer having one end confronting said drum, a first lever having animpact surface and pivoted to the opposite end of said hammer, means tomount and to constrain the movement of said hammer in excursions towardand away from said drum, a mounting plate, a second lever having animpact surface and pivoted to said plate for movement in a planecoplanar with the plane of said first lever, said second lever having afirst arm opcratively associated with said first lever to form acooperating lever system, resilient means operatively connected with alever of said system in a manner such that said levers are normallybiased to a print position, a cam adapted to strike the impact surfaceof one of said levers and thereby drive said hammer toward said drumwhen said levers are in said print position, said cam also adapted tostrike the impact surface of the other of said levers to position saidlevers in a non-print position after said hammer is driven toward saiddrum, said second lever having a second arm, a stationary permanentmagnet structure adjacent to said second arm, an armature attached tosaid second arm, said armature holding said lever system in saidnon-print position against the force of said resilient means when saidarmature is in engagement with said permanent magnet structure, abucking coil associated with said permanent magnet structure, and saidcoil when energized adapted to reduce the armature-holding force of themagnet structure an amount snlficient to release the armature under theinfluence of said resilient means thereby enabling said resilient meansto pivot the levers of said lever system to said print position at whichsaid cam sequentially engages said levers.

2. The subject matter of claim 1 wherein said permanent magnet structureincludes a permanent magnet core, a pair of pole pieces in flux linkagewith said core and having a pair of spaced free ends, and said armaturebridging said free ends when engaged with said permanent magnetstructure thereby forming a closed-loop magnetic circuit.

3. The subject matter of claim 2 wherein one of said pole pieces iscomposed of a part of said mounting plate.

References Cited by the Examiner UNITED STATES PATENTS 2,056,745 10/36Stalmaker 317-172 2,178,289 10/39 Snavely a- 317172 X 2,766,686 10/56Fomenko et a1. 2,892,954 6/59 Orlando 317-172 2,897,752 8/59Nlfiln'llOS.

2,930,889 3/60 Hours 317172 2,949,846 8/60 Hoffman et al. 3,049,990 8/62Brown et a1.

WlLLIAM B. PENN, Primary Examiner.

1. IN AN ELECTROMECHANICAL PRINTER HAVING A PRINT DRUM, A MOVABLE PRINTHAMMER HAVING ONE END CONFRONTING SAID DRUM, A FIRST LEVER HAVING ANIMPACT SURFACE AND PIVOTED TO THE OPPOSITE END OF SAID HAMMER, MEANS TOMOUNT AND TO CONSTRAIN THE MOVEMENT OF SAID HAMMER IN EXCURSIONS TOWARDAND AWAY FROM SAID DRUM, A MOUNTING PLATE, A SECOND LEVER HAVING ANIMPACT SURFACE AND PIVOTED TO SAID PLATE FOR MOVEMENT IN A PLANECOPLANAR WITH THE PLANE OF SAID FIRST LEVER, SAID SECOND LEVER HAVING AFIRST ARM OPERATIVELY ASSOCIATED WITH SAID FIRST LEVER TO FORM ACOOPERATING LEVER SYSTEM, RESILIENT MEANS OPERATIVELY CONNECTED WITH ALEVER OF SAID SYSTEM IN A MANNER SUCH THAT SAID LEVERS ARE NORMALLYBIASED TO A PRINT POSITION, A CAM ADAPTED TO STRIKE THE IMPACT SURFACEOF ONE OF SAID LEVERS AND THEREBY DRIVE SAID HAMMER TOWARD SAID DRUMWHEN SAID LEVERS ARE IN SAID PRINT POSITION, SAID CAM ALSO ADAPTED TOSTRIKE THE IMPACT SURFACE OF THE OTHER OF SAID LEVERS TO POSITION SAIDLEVERS IN A NON-PRINT POSITION AFTER SAID HAMMER IS DRIVEN TOWARD SAIDDRUM, SAID SECOND LEVER HAVING A SECOND ARM, A STATIONARY PERMANENTMAGNET STRUCTURE ADJACENT TO SAID SECOND ARM, AN ARMATURE ATTACHED TOSAID SECOND ARM, SAID ARMATURE HOLDING SAID LEVER SYSTEM IN SAIDNON-PRINT POSITION AGAINST THE FORCE OF SAID RESILIENT MEANS WHEN SAIDARMATURE IS IN ENGAGEMENT WITH SAID PERMANENT MAGNET STRUCTURE, ABUCKING COIL ASSOCIATED WITH SAID PERMANENT MAGNET STRUCTURE, AND SAIDCOIL WHEN ENERGIZED ADAPTED TO REDUCE THE ARMATURE-HOLDING FORCE OF THEMAGNET STRUCTURE AN AMOUNT SUFFICIENT TO RELEASE THE ARMATURE UNDER THEINFLUENCE OF SAID RESILIENT MEANS THEREBY ENABLING SAID RESILIENT MEANSTO PIVOT THE LEVERS OF SAID LEVER SYSTEM TO SAID PRINT POSITION AT WHICHSAID CAM SEQUENTIALLY ENGAGES SAID LEVERS.